Anticollapsing hydraulic lifting cylinder system for tier-lift trucks



prll 27, 1954 E, J, ABBE ANTICOLLAPSING HYDRAULIC LIFTING CYLINDER SYSTEM FOR TIERLIFT TRUCKS Filed Sept. 7, 1950 R. n 2 m a@ ,www m 0,8 MJ. W

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Patented Apr. 27, 1954 ANTICOLLAPSIN G HYDRAULIC LIFTING CYLINDER SYSTEM FOR TIER-LIFT TRUCKS Edward J. Abbo, Cleveland Heights, Ohio, as-

signor to The Elwell-iarker Electric Company, Cleveland, Ohio, a corporation of Ohio Application September 7, 1950, Serial No. 183,593

2 Claims. l

This invention is directed to improvements in hydraulic lifting cylinder systems for tier-lift trucks. The general object of the invention is the provision of an hydraulic lifting cylinder system for operating the load elevating mechanism of an industrial truck in which the load lowering stroke is automatically controlled in its rate of return.

Another object is the provision of a mechanism having a controlled rate of return stroke in which means for controlling the return stroke rate is incorporated within the hydraulic cylinder unit for protection of the control means and compactness of construction.

With the above and other objects in View, which will be apparent from the detailed description which follows, the invention consists certain novel features of construction and combination oi parts which will be readily understood by those skilled in the art to which the invention appertains. In the drawing, which illustrates an embodiment of the invention- Fig. l is an elevational view in partial axial section of an hydraulic lifting cylinder system incorporating the present invention;

Fig. 2 is a fragmentary enlarged axial sectional view taken along the line 2 2 of Fig. l, showing in detail the reverse flow control means for the hydraulic cylinder system; and

Fig. 3 is a View, similar to Fig. 2, of another form of reverse ow control means.

The present invention contemplates the use of new control valve similar to a check valve in the fluid passage of an hydraulic cylinder mechanism of a tier-lift truck to control the rate of the travel of the loading elevator in its lowering stroke, the control valve as hereinafter described being adapted to allow free flow of hydraulic nuid in one direction for a lifting operation, but to limit the reverse stroke flow during lowering of the load. Although such flow control means is shown in the drawings incorporated in a compound hydraulic cylinder mechanism such as that disclosed in co-pending application Serial No. 134,098, led December 20, 1949 (the cylinder system alone being shown here), the present invention may be utilized for other hydraulic cylinder systems, either of the single or multiple cylinder type. As disclosed in the abovementioned zzo-pending application, the hydraulic cylinder system here shown is intended principally for use in a telescoping frame type lift truck in which a primary movement in the cylinder system causes the lifting of a load-carrying platform riding Von the movable part of the telescoping frame and a secondary movement of the cylinder system causes the elevation of the movable part of the frame, and hence further lifting of the load carriage also. An inner or secondary cylinder plunger tube I0, closed at its lower end by a channelled plug Il, slides in the tube i2, closed at its upper end by the cylinder head or plug I3, the two tubes forming a piston and cylinder unit for producing the abovementioned movement. The plug Il, which also serves as a member for mounting the whole compound cylinder unit to a truck, is provided with a transverse bore I4 which pivots about a stud carried by the truck frame. A threaded aperture l5 is provided in the side of the plug for hydraulic piping to bring hydraulic fluid under pressure to the cylinder system and it communicates with the interior central channel I6, into the end oi which is threaded a control device, generally indicated Il and hereinafter described in detail. The upper end of tube lll is provided with a guide ring i3 sliding on the inner wall of the tube l2 and retained in place by a split spring ring i9. The cylinder head or plug i3, threaded into the upper end of tube I2, has a reduced threaded extension 2l for mounting the upper part of a telescoping frame and also has an air bleeder channel 22, closed by the plug bolt 23. The lower end of tube i2 carries a head structure 24 with associated packing nut 25 and packing 2S which serve to slidably seal tube l2 on tube It. Toward the upper end of tube I0 an outwardly projecting stop 2l near the upper end of tube It limits the travel of these tubes relative to each other in the secondary movement of the cylinders by abutting against the shoulder-like portion 28 formed by the upper end of the head.

An outermost cylinder 30, which at its lower end is threaded onto the head structure 213 in spaced relation from tube l2, acts as a primary cylinder in conjunction with the tube 3i disposed between the tube 3l! and the tube i2. The upper end of the primary cylinder plunger tube 3i is closed by another head structure 32, packing and gland nut 34 while its lower end is held in concentrically spaced relation to the tube it by the sliding guide ring 35 provided with longitudinal oil channels 3B. The upper end of the primary cylinder tube 30 is closed and held in slidable sealed relation to the tube 3i by the head structure 38, packing 39 and gland nut dit. A stop 4i at the lower end of primary cylinder plunger tube 3i, upon abutting against the head structure 33, vlimits the primary stroke. An air bleeding channel 43 for the hydraulic cylinder Sil,

closed by a nut 44, is provided in the side of the head structure 38. To allow for passage oi fluid from one cylinder to another, an aperture d is provided for tube I whereby the interior of tube I0 communicates with the space between tubes I0 and I2. Likewise an aperture il is provided in the tube I2 for communication from the space between tubes l0 and I2 to that space between tubes l2 and 3|. On the exterior of the primary cylinder 3D lugs or ears 50 with bolt holes d! are provided for attaching cables or chains which are connected at their other ends to the load-lifting carriage of the truck in which this cylinder system is used. Usually upon the shoulder formed by the top edge of the head structure 32 there rests a yoke carrying sheaves over which are passed the cables or flexible chains connecting the primary cylinder and the load carriage.

The iiow control device, indicated generally by the reference numeral II in Fig. l and shown in detail in Fig. 2, comprises a control valve casing 6i! and a movable valve member iii, having a hollow cylindrical stem 62 sliding in an axial bore 53 of the casing and a head portion 55. The cylindrical stem 62 is provided with longitudinal port slots d while the head portion 55 has a small orice 66 and a beveled portion el adapted to seat on correspondingly beveled seat portion 68 formed in the va-lve body. Above the seat Sii, an enlargement 59 of the body bore provides clearance about the valve head. rThe lower end of the body is threaded to receive a close nipple I0 connecting the control device to the upper internally threaded end of the channel l5 in the plug I I. The other end of the valve body is threaded to receive a valve member retainer 'il provided with lugs l2, by which the head of the valve member is spaced from the outlet channel 'i3 to insure free flow of hydraulic iluid into the cylinder system. The upper end of retainer 'li has an hexagonal outer form to provide wrench purchase in turning the flow control assembly into the plug II. A spring 14, supported at its lower end by the spring retainer 15, bears against the lower end of stem 62 to urge the valve member to open position.

Thus, when hydraulic fluid is admitted under pressure through the aperture I5 and the channel it it passes through flow control device I'! in an unrestricted manner, the valve member 6I being lifted from its seat (as in Fig. 2), into the inner bore of tube Hl, through the aperture and i'l and through the longitudinal apertures Se in the guide 35, causing the primary plunger tube SI to move upwardly in the above mentioned primary motion, thereby moving the sheaves of the carriage cable system with respect to the ears 5E) to elevate the load carriage. When the stop il abuts against head 3B the primary motion is stopped and continued fluid pressure will then extend the secondary cylinder unit by causing tube I2 to slide upward on tube It, carrying the extended primary cylinder unit with it. When hydraulic pressure is released, however, and the cylinder system tends to collapse under the weight of the telescoping frame, the reverse flow o the hydraulic fluid through the control device il, urges the valve member 5I toward the seat against the force of spring 1li, so that reverse flow takes place through an eiective flow opening which may vary to control the reverse flow and rate of descent of the telescoping frame and load carriage of the truck. The strength of spring 'le is chosen to determine the maximum flow rate, and hence cylinder collapse rate as desired. If a heavy load is on the carriage of the truck when the supporting hydraulic pressure is cut off, the initial reverse flow surge is impeded by the seating of the valve member, allowing flow only through orice 66, to prevent a sudden dropping of the loaded elevating system. Thereafter, ow may continue through the orifice 66 if the load is quite heavy, or the valve member may open somewhat under the action of spring 'M to allow flow through ports 64.

Another form of control device which may be used is shown in Fig. 3. The body B0 is bored axially from each end, the bores, however, not meeting; while part of the body length is turned down to provide a channel BI formed between the sleeve 32 and the body, the channel serving to connect the radial ports 83 opening to the bottom bore 8d and radial ports S5 opening into the upper bore 85. The sleeve 82, with its upper end abutting against shoulder 8l is held in place by a split ring 83 in a groove on the body, while packing 89 and` zit seal the upper and lower ends of the sleeve to the body. A hollow piston 9i, provided with an end opening S2, and circumerentially extended valving slots S3, serves as a valving member movable in the upper bore as a cylinder. A compression spring 9G urges the piston upward to fully open position against stop 555, a split ring expanded into a groove in the cylinder wall. In the open position the slots ports 85 are in correspondence. The lower bore Sli is threaded to receive the close nipple connecting the control device to plug l l.

lll/hen hydraulic fluid is iiowing into the cylinder system it passes freely through channel I6, the valve inlet bore 86, ports 33, the cylindrical channel 8l surrounding the body, the ports 85,

-valving slots 93, aperture 92, and out the upper bore ilii into the hydraulic cylinder space, as shown by the now lines in Fig. 3. When hydraulic pressure is released, so that the cylinder system tends to collapse under the applied load, the upward bias of the spring 94 tends to keep the piston in open position despite the reversed iiow as long as the reverse flow is not too great,

that is as long as the cylinder system is not contracting too fast. With higher reverse ilows, cor- `esponding to greater rate of lowering of the load carriage and telescoping frame in a tier-lift truck, the piston 9i tends to move downward, thereby displacing the va-lving slots $23 with respect to ports 85 and hence closing the valve to some degree to decrease the flow. With a heavy reverse flow surge through the piston 9i the piston will move downward against the spring far enough to close ofi the flow, hence preventing a sudden drop of the load supported by the cylinder system. Then the spring will return the piston to some open position to allow a controlled reverse iiow from the cylinder system, and hence a controlled rate of descent of the load eleva-ting mechanism of the truck.

I claim:

l. For a hydraulically operated load elevating mechanism of an industrial tier lift truck, a hydraulic cylinder system adapted for extension against a load by supply of hydraulic liquid pressure thereto and for controlled contraction rate under said load upon release of said fluid pressure including a cylinder member, a piston member movable in the cylinder member, one of said members having formed therein a hydraulic liquid conduit opening interiorly of the cylinder system for introducing hydraulic liquid into the working iiuid space between the said members and exteriorly for connection to a supply of such hydraulic liquid, and a flow control valve disposed interiorly of the two said members in said having in the other end a uid channel opening` interiorly of said bore through apertures radial thereto and connected exteriorly to the inner end of said conduit, a hollow valve member sideable in said bore, said valve member having radial apertures registrable at an open position with the apertures of the body, and spring means in said bore biasing the said member outwardly to said open position to permit free iiow of liquid into said system in extending the said members relative to each other, and said valve member hav ying an axial passage provided with a constriction opening from said apertures of the valve member outwardly to said bore, whereby liquid flow upon contraction of said system tends to displace said valve member from open position against the bias of said springs to limit the rate of contraction of the system.

2. A hydraulic cylinder system adapted for extension against a load by supply of hydraulic liquid pressure thereto and for controlled contraction rate under said load upon release of said uid pressure including a cylinder member, a piston member movable in the cylinder member, one of said members having formed therein a hydraulic liquid conduit opening interiorly of the cylinder system for introducing hydraulic liquid into the working fluid space between the said members and exteriorly for connection to a supply of such hydraulic liduid. and a flow control valve disposed interiorly of the two said members in said space and connected to the inner end of said conduit; said valve comprising a valve body having therethrough liquid passage means including a bore extending part way in from one end and having in the other end a uid channel opening interiorly of said bore through apertures radial thereto and connected exteriorly to the inner end of said conduit, a hollow valve member slidable in said bore, said valve member having radial apertures registrable at an open position with the apertures of the body, and spring means in said bore biasing the said member outwardly to said open position to permit free flow of liquid into said system in extending the said members relative to each other, and said valve member having an axial passage provided with a constriction opening from said apertures of the valve member outwardly to said bore, whereby liquid ow upon contraction of said system tends to displace said valve member from open position against the bias of said spring to limit the rate of contraction of the system.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 635,848 Dutton Oct. 31, 1899 820,701 Coleman May 15, 1906 824,425 Johnson June 26, 1906 1,840,311 Du Bois Jan. 12, 1932 2,418,325 Wassall et al. Apr. 1, 1947 FOREIGN PATENTS Number Country Date 598.406 Germany June 9. 1934 

